Several bacterial tRNA species will be purified to homogeneity and their solution structure and dynamics will be analyzed by high resolution NMR spectroscopy. The divalent cation sites and thermal unfolding sequence of these tRNAs will be studied. The interaction of substrates with three thermophilic aminoacyl-tRNA synthetases will be studied by classical equilibrium binding methods and conformational changes in synthetase-tRNA complexes will be probed by NMR spectroscopy.